Theresa May said the decision on airport expansion would be made "shortly" at the Conservative Party Conference (Source: Getty)

Rebecca Smith

The government is set to decide on airport expansion in the south east next week, as legal experts warn that a lengthy process means consent is not likely to come before 2020 - an election year.

Kevin Gibbs, planning partner at Bond Dickinson who has advised on airport expansion since the government’s 2003 whitepaper, The Future of Air Transport, told City A.M.: “The government has made it very clear that any major air expansion or new runway is going through a Nationally Significant Infrastructure Project (NSIP) process and the earliest an application may come forward is probably 2018 and consent achieved not before 2020 at the earliest.”

He pointed out that this would also be the year of the next general election under the fixed-term Parliaments Act.

The government has said the decision on airport expansion would come this month, with the 18 October considered the likely date for the announcement.

Both Heathrow and Gatwick have been lobbying their cause; the latter has just written an open letter to MPs urging them to back a second runway at Gatwick. “Successive governments have tried and failed to expand Heathrow and given the insurmountable noise and air quality it faces, a decision for Heathrow will inevitably lead to more delays and stalled growth.”

The discussion of granting both Heathrow and Gatwick the green light in some shape or form has though, been welcomed by Gatwick. The airport feels it would have first mover advantage and get a five to ten year head start on Heathrow due to the construction, legal and financial challenges Gatwick expects Heathrow’s third runway to have.

It comes as the Royal Borough of Windsor and Maidenhead yesterday agreed to spend £50,000 to launch a legal challenge (topping up the budget by £20,000) if the government decided to grant Heathrow a third runway. It had already teamed up with local authorities in Hillingdon, Richmond and Wandsworth in a proactive effort to block the potential development.

Councillor Derek Wilson, cabinet member for planning, said: “If Heathrow expands it will come with a greater number of people and vehicles using our already strained infrastructure. With today’s support from the cabinet prioritisation sub committee we and our partners in Hillingdon, Richmond and Wandsworth remain committed to fighting expansion at Heathrow.”

It is understood Heathrow has factored in the time for legal challenges in its planning – anticipating they would run alongside the other processes – and see the overall time scale being four years, from the decision being made by the government, to the actual construction work commencing.

Another option for airport expansion that has been bandied around involves Birmingham Airport also being granted expansion. The Airport is compiling a master plan that's being drawn up by a range of internal departments to show what the airport will look like in the future. A spokeswoman for the airport said the plans aren't being disclosed externally yet.